As a test I have set shipping calculation as:
Order weight from: 0kg
Order weight to: 100kg
Use percentage: N
Charge percentage (per subtotal): 0
Charge amount per kg: 3
However my shipping calculation keeps showing as $0
I have checked that the user is not entitled to free shipping, and free shipping is not enabled for the product, nor is there a discount with free shipping enabled.
In fact, even when I set a "Additional shipping charge: $10" in the product variant (SKUs) options no shipping is shown.
What might I have done wrong?